Process of producing ferricyanides



Patented Aug. 23,1932

UNITED STATES WILHELM GLUUD AND normal) KELLER, or DoRrMUNn-nvme, GERMANY PROCESS OF PRODUCING FERRIQYANIDES No Drawing. Application filed June 5, 1928, Serial No. 283,120, and in Germany m .15, 1927.,

Our invention refers to the production of ferricyanic acid and more especially to a method of producing this acid or its compounds from ferrocyanic acid or the compounds thereof.

Ferrocya-nic acid and itscompounds have already been oxidized in several ways, however, this oxidationv was hitherto possible only with the aid of very powerful oxidizing agents, such as chlorine, lead peroxide and potassium permanganate.

We have now found as the result of many experiments that ferrocyanic acid and its compounds can be converted into ferricyanic acid and its compounds also with the aid of oxygen or gases containing oxygen, if the process is carried out in a certain manner.

We have found that if calcium ferrocyanide is exposed in watery solution under increased pressure and at moderate temperature to'the action of air, it will be completely converted into calcium ferricyanide, according to the formula ca, Egon 6) 2+ oagon As shown by this formula, the conversion results in an alkaline solution which exerts a destructive influence on the product of reaction. It is therefore necessary to add an acid, preferably a weak acid. If the gas containing oxygen, which isallowed to act on the calcium ferrocyanide, still contains carbon dioxide, no further addition of acid is required. We may, however, also add a weak acid, such as acetic acid or oxalic acid, to the solution from the beginning.

The oxidation can be effected with clifierent kinds of gas mixtures containing oxygen,

40 but also with pure oxygen. The well known processes for the production of ferrocyanic acid and its compounds from cyanogen and from cyanides may of course be combined with the process according to'the present invention so that ferricyanic acid and its compounds can be produced in a continuous operation from cyanogen or from cyanldes.

anide (calculated for Ca Fe(CN) (211 0)) is treated in an autoclave at atemperature 0f'80100 C; with compressed air containing 7 5 per cent carbonic acid, theoperatingpres3 sure being 80420 atms,

The following figures illustrate the course of the oxidation independency from tlme.

100 coins. of the solution contained Ferricya- Dura- Temperan e Oxidized tion of ture in calculated ferrotest centi-' Ca2Fe 08.3(F6- as ierrocyanide minutes grades (CNM- (0N)u)zcyanide per cent (21120) (21120) grams (s r I II I II I II I II I II I II limits and that the temperature and pressure as well as the starting materials may be varied greatly. The expressions ferricyanide and ferrocyanide used in the following claims are intended to designate all compounds, including acids, bearing the ferricyanide or ferrocyanide radicle, respectively.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

We claim:

1. The process of converting a ferrocyanide to ferricyanide which comprises passing a gas comprising free oxygen through a solution of the ferrocyanide under elevated pressure and temperature in the presence ofacid.

2. The process of converting a ferrocyanide to ferricyanide which comprises passing a gas comprising free oxygen through a solution of the'ferrocyanide under elevated pressure and temperature in the presence of a weak acid.

3. The process of converting a ferrocyanide to ferricyanide which comprises passing a gas comprising free oxygen through a solu tion of the ferrocyanide under elevated pressure and temperature in the presence of carbonic acid. 7

ide to ferricyanide'whic'h comprises passing 15 air containing. carbon dioxide througha so-- 4. Therprocess of converting a ferrocyanide to ferricyanide which comprises passing a gas comprising free oxygen through a solution of the ferrocyanide under elevated pressure and temperature in the presence of acetic acid. 7 r

5. The process of ="converti'ng a'- -fei'rocyan. ide to ferricyanide which com rises passing a gas comprising free oxygen 1; roughasolu tion of the ferrocyanide under-elevatedpres 2 sure and 301d.

temperature in the presence of oxalic 6. The process of converting a ferrocyan liition of thejierrocyanide under apre'ssureof fro'mSO to 12,0 atmospheres and at a tempera tnie of'from 80 to l 00"centi-grade'.

In testimony whereof "we afliii our: signa- WWW CERTIFICATE OF CORRECTION.

atent No. 1,872,929. August 23, 1932.

WILHELM GLUUD ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 69, in the table, 10th column, for "6425" read 6.25; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of October, A. D. 1932.

M. J. Moore, Seal) Acting Commissioner of Patents. 

